I have recently aquired a frame that has a split in the bottom of the head tube The split has cracked the bottom lug and about 1/2" of the tube.It looks like someone has placed a bar inside the head tube to increase leverage whilst removing a stubbon seatpost

I thought that I would try to salvage the frame which is quite a nice one by brazing a new piece of tube inside the existing head tube to reinforce the split which i shall also braze .

I am torn between inserting the new section of tube for the full height of the existing head tube and then turning down the two headset cups so that they fit within the slightly reduced head tube internal diameter or:-

Braize the new tube to the bottom headset cup first (steel cups)and then braize both inside the existing headtube.

Naturally either option will mean that the frame will have a limited lifetime of the life of the headset bearing surfaces but i'd be hapy to get a year out of the frame rather than throw it away.

Has anyone by chance got a 2" length of silver solder by any chance ? I guess jewelers use it.

Last edited by peanut on Wed Aug 26, 2009 10:10 am, edited 1 time in total.

an outside hoop is not a bad idea .I hadn't really thought of that. I suppose I thought of an internal hoop because it wouldn't show.
My idea is to use a steel headset cup as an internal hoop and braze it into the bottom of the headtube. It would need careful jigging to keep it perfectly in alignment

edit:- I justr checked the frame and unfortunately the headtube doesn't extend enough to put an external band on. It looks to me like the headtube has been faced and lost about 1/8" of both ends

If I can do the brazing without damaging the paintwork other than the headtube it might be worth a go. If I had to replace the headtube and lugs I wouldn't attempt it. The frame isn't worth it .

I will be doing the brazing myself .it needs a skilled hand and a delicate touch and I have been brazing pipes for 40 years. Its also a bit of a challenge which is why I am doing it. I enjoy salvaging things that have been discarded.

If the split is at the front of the headtube, why not just braze a strap around the front?
Possibly the best thing to do is grind back the entire front face of the lug, then fit a patch section around the outside for say the bottom 15mm. You will doubtless also have the ability to fillet around the repair section to make it look nice!

If the split is at the front of the headtube, why not just braze a strap around the front?Possibly the best thing to do is grind back the entire front face of the lug, then fit a patch section around the outside for say the bottom 15mm. You will doubtless also have the ability to fillet around the repair section to make it look nice!

that operation is too fiddly and would require too many areas to selectively heat. i think you'd have the silver solder run out of everwhere too quickly by by the time you had finished.

An external ring would be better because it doesn't rely on the solder for structural integrity
A ring is intrinically strong .

This part of the frame takes almost as much stress as the BB I reckon.
I'm going to go with the internal solution and actually use a steel headset cup and braze it into the bottom of the head tube. That way nothing will show on the outside and it shouldn't damage any adjacemt finish on the other tubes hopefully.

What's the frame tubing? I thought that only 653 and 753 required silver, the rest brass brazing was fine.
Admittedly, you might introduce plenty of other problems by heating to beyond the melting point of the existing braze...

I agree that it's a dangerous area to muck about with - the forks act as a lever to open up the head tube at the best of times.

you can use silver solder on any bike frame tubing. Its was used on 753 to reduce the heat required to braze from degrading the tube strength.

Its much easier to use SSolder when you need to do a localised joint and don't wish to heat the whole lug and lose the braze in adjacent tube joints because silver solder melts at a much lower temperature than brass .

I love using solder because it runs and flows quickly and wets the surfaces well forming a strong bond even when the jointed surfaces are not perfectly clean. Its easier to see flow so you know you have a good joint

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